Fig. 1.

Nerve biopsy, MRI findings, and intraoperative photos.

Nerve biopsy, MRI findings, and intraoperative photos: (A) Epoxy resin section of the nerve, magnification x400. Axonal loss associated with numerous macrophages engulfing degenerating nerve fibers. (B) Electron microscopy, original magnification x5000. A macrophage appears to be stripping myelin sheath. (C) MRI FLAIR: normal intensity of the posterior interosseous branch of the radial nerve prior to the supinator tunnel, left, and increased intensity within the supinator tunnel, right. (D) MRI neurogram demonstrates enlargement and increased T2 hyperintensity of right sciatic nerve (white arrow). (E, F) MRI neurogram demonstrates increased T2 hyperintensity seen in the roots of the brachial plexus bilaterally (white arrows) in the same patient. (G) Intraoperative photos pre- (left) and post-surgical decompression (right) of the posterior interosseous branch of the radial nerve at the Arcade of Frohse.

Abbreviations: FLAIR - fluid-attenuated inversion recovery